Flash-forward. Jack drives his jeepy thing down a street in a poor part of town, blasting his radio at top volume. Rude. He parks and kills the music. He's across the street from the funeral home from last season's finale. He walks up to the door and tries to open it. It's locked, because it's the middle of the night. So Jack picks up a brink and smashes the doorknob off the door and then kicks the door in. He sees the coffin there. The body release form that is conveniently sitting on top of it confirms that the coffin is housing Jeremy Bentham. Jack opens the lid, but we don't see inside. Yet. A voice says Jack's name. He jumps, startled, and the voice apologizes. It's Ben, looking quite dapper. Ben asks if "he" told Jack that Ben was off the island. He did. Ben asks when Jack spoke to him. It was about a month earlier. And Kate also spoke with him. Ben asks what he told Jack, and Jack responds, "He told me that after I left the island, some very bad things happened." Ah, but before you left the island some very bad things happened. Jack continues, "And he told me it was my fault, for leaving. And he said that I had to come back." Ben has heard about Jack's flights over the Pacific. Jack asks why he's there. Ben: "I'm here to tell you that the island won't let you come alone. All of you have to go back." Jack thinks that's not happening -- he doesn't know where Sayid is, Hurley's insane, Sun blames him for Jin's death, and Kate won't speak to him. Ben thinks he can help with those problems, because they have to go back together. Jack nods his head. He starts to walk to the door of the funeral home. Ben stops him: "Jack, I said all of you. We're going to have to bring him, too." They look at the coffin. And then the camera pans across the top of it. The dead body inside is Locke. Credits.
Just to sum up, Locke, Juliet, Sawyer, Rose, Bernard, and Claire are still on the island. Michael has to be dead, having been right in the room when the C-4 blew up. I think it's extremely likely that Jin is dead -- the only way he could have survived is if he was able to jump off the freighter before it exploded, avoided the flying debris and fuel, and was pulled along with the island when it moved. Because otherwise, even if he survived the explosion, he would have been trapped in the water without a boat and no place to swim to. Finally, the status of Daniel and his group of no-names is uncertain -- I'm assuming they must have been close enough to the island to be moved with it, but there's no definite evidence of that.